Importance of blood samples for diagnosis and drug sensitivitytesting in HIV positive patients with suspected tuberculosis.
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Date
2004-04
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Abstract
Background: Diagnosis of tuberculosis is difficult in HIV positive patients since they often present with atypical
symptoms and are susceptible to pulmonary infections that mimic tuberculosis. Sputum collection may not be possible
even in patients with pulmonary involvement since a productive cough is not always present. In such patients, blood
smear and culture for AFB apart from serving as a diagnostic tool can be used for testing drug sensitivity.
Objectives: This study was undertaken to explore the value of blood culture for diagnosis in patients with suspected TB. In
addition, a comparison of drug sensitivity patterns of blood and sputum isolates in 10 of these patients was also carried out.
Methods: Blood and sputum samples were processed, cultured and isolates tested for their drug susceptibility and for
niacin production, nitrate reduction as well as catalase activity at 68o C.
Results: All 24 blood samples were culture positive although only 6 were smear positive. On the basis of the biochemical
investigations, 22 strains were identified as Mycobacterium tuberculosis. All the 10 sputum samples were culture
positive despite 4 being smear negative. Comparison of drug sensitivity profiles from blood and sputum revealed
concordance to five first or second line drugs in 5 of 10 patients. Additionally, 2 patients demonstrated discordance for
only one first or second line drug.
Conclusion: The study demonstrates the importance of blood culture in confirming diagnosis of tuberculosis and
testing for drug sensitivity in HIV positive patients without a productive cough. The level of discordance in drug
sensitivity profiles between blood and sputum the same individual is suggestive of infection with multiple strains.
Testing for the occurrence of multistrain infections through individual colony examination of a single isolate is
necessary since such infections would affect treatment of non-responder patients having HIV-TB dual infections.
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Keywords
HIV and TB, Diagnosis of Drug sensitivity Testing
Citation
D'souza Desiree T B, Birdi Tannaz J, Dholakia Yatin, Hira Subhash, Antia Noshir H. Importance of blood samples for diagnosis and drug sensitivitytesting in HIV positive patients with suspected tuberculosis. Indian Journal of Tuberculosis. 2004 Apr; 51(2): 77-81.